1. Field of the Invention
The present invention relates to a solid filling tank in which solid particles capable of absorbing or adsorbing a gas such as a hydrogen gas, are filled.
2. Description of the Related Art
As well as heat of solar light, there is given a great attention to hydrogen as clean energy source. Especially in developing a fuel system for a hydrogen fuel cell vehicle, attention is focused on a technology to effectively store and discharge hydrogen by utilizing a hydrogen absorbing alloy that absorbs hydrogen. As for a particular example of such technology, there is known a technology to fill hydrogen absorbing alloy powders in a storage tank (hydrogen storage tank), and to cause the hydrogen absorbing alloy powders in the storage tank to absorb and store the hydrogen and to discharge for utilizing the hydrogen. The hydrogen absorbing alloy has the characteristic that generates heat when absorbing hydrogen and absorbs heat when discharging the hydrogen. Therefore, a heat exchanger is normally disposed in the hydrogen storing tank as a mechanism for absorbing or discharging the hydrogen. For example, a heat exchanger is employed having such a structure that a plurality of heat-transferring fins are arranged in a manner like the teeth of a comb on an outer periphery of the cooling/heating medium tube through which the refrigerant or the heating medium is circulated. There is disclosed in JP-2000-111193 (particularly in paragraphs [0011] and [0012]) another type of heat exchanger having the structure that circulation paths through which the refrigerant or the heating medium is circulated are configured by using combination of corrugated plates and flat plates in place of the cooling/heating medium tube in the aforementioned heat exchanger.
The hydrogen absorbing alloy has a property that expands when absorbing hydrogen. Therefore, when the filled hydrogen absorbing alloy powders absorb hydrogen in a state subsided and consolidated in the storage tank, in some cases, an excessive stress is locally generated against a tank main body due to the expansion of the hydrogen absorbing alloy and the stress influences on a tank main body of the storage tank or on a lining member disposed in the storage tank. For this reason, as the measure against such problem, there has been proposed a technology to provide a structure to prevent the subsidence of the hydrogen absorbing alloy powders. There also has been proposed a structure to absorb the stress caused by the hydrogen absorbing tank when absorbing the hydrogen. As for such technology, a first technology and a second technology described in the following have been conventionally proposed.
In the first technology, as described in JP-11-043301 (particularly in paragraph [0009] and in FIG. 2), a sheet member is provided between a plurality of fin-shaped tubes constituting a heat exchanger, whereby the subsidence of the hydrogen absorbing alloy powders is prevented. In the second technology, as described in JP-2001-010801 (particularly in paragraph [0024]), the subsidence of the hydrogen absorbing alloy powders is prevented by a cooling/heating medium tube having a hollow pipe structure and having a sectional shape configured to be an ellipse.
According to the first technology to provide the sheet member between a plurality of the fin tubes, the subsidence of the hydrogen absorbing alloy powders can be prevented. However, extra space to provide an extra member such as the sheet member is needed in the tank main body of the storage tank. Thus, a filled volume of the hydrogen absorbing alloy powders (gas absorbing solids) and a space for the heat exchanger need to be reduced correspondingly. Also, in the first technology, since a plurality of the fin tubes and a plurality of the heat-transferring fins are arranged in cross-sectional direction of the tank main body of the storage tank, the heat-transferring fins, in between the fin tubes, do not come into contact with the hydrogen absorbing alloy powders in many areas. Therefore, in the first technology, the subsidence of the hydrogen absorbing alloy powders in the tank can be prevented, whereas reduction in the heat exchanging performance between the hydrogen absorbing alloy powders and the heat exchanger becomes a problem. In the second technology, the problem in the first technology can be overcome by preventing the subsidence of the hydrogen absorbing alloy powders by use of the cooling/heating medium tube. Nevertheless, there is the limit to prevent the subsidence of the hydrogen absorbing alloy powders since the cooling/heating medium tube has the R portion (curved portion). Therefore, it is hard to say that the second technology is the exact approach.